Ground Loop Issue 427


After talking with the manufacturer's of both the amps & preamp, I still have a 60hz hum. Here's the story:

Just changed amps to 845 SET monos, and now I hear the hum whenever the amps are on and RCA interconnects are connected to the amp inputs. Didn't have the problem with two prior pairs of amps. The pre could be turned off, and I still hear the hum. With shorting plugs in the amps, no hum.

The pre is battery powered, with no ac cable, and the trouble persists whether or not any sources are connected to the pre.

I've tried multiple types of interconnect, including the heavily-sheilded cheapos from a vcr, but no change.

One friend questions if adding a "hum potentiometer" to the amps would make sense. Others have suggested the $600 Granite Ground Zero, which is unaffordable for me.

I've already tried cheater plugs any/everywhere. I've added a grounding wire between the monoblocks metal bottom plate and floating one power cable while leaving the other grounded, all per the amp manuf's suggestion. I've tried HighWire LiveWires, which might be good sonically for RFI, but aren't helping the hum issue. This is a music only rig, no cable tv anywhere in the room. I am in a heavy RFI area, 1000ft from a radio tower, if that matters...

Anybody got any suggestions other than moving elsewhere? Thanks,

Spencer
128x128sbank

Showing 2 responses by jb0194

Call Jensen Transformers (do a web search) and buy an "Isomax". It'll cost under $200, but also require an additional interconnect pair. They use very high quality isolation transformers. The box is about 3"x5"x1" size.

I've found the "Isomax" to sufficiently mitigate hum in my systems. When it's failed, nothing else "worked" either. I've also found that Cardas Golden Reference ICs screen hum better than any I've used, though I'm sure many others do as well - but many don't.

Good luck. I despise hum/noise.
Nope, the cheapo stuff on Ebay, etc. has nothing in common with the Isomax. Again, no guarantees, but the Jensen's a very high quality item.